The first of two stages this weekend predicted to go a long way towards deciding the overall winner of the 2013 Giro d'Italia was thrown into chaos by the poor weather that has dogged this year's race, with the climb to Sestriere cancelled - but it ended with Astana's Vincenzo Nibali tightening his grip on the maglia rosa, the Sicilian finishing second to Vini Fantini-Selle Italia's Mauro Santambrogio on the Stage 14 summit finish of the Jafferau.

An attack from Nibali inside the final 2km blew the GC group apart, he and Santambrogio, followed by AG2R's Carlos Betancur, sweeping up three remaning breakaway riders. Besides cold, driving rain, low cloud meant that not only the helicopters that provide aerial TV coverage of the race, but also the aeroplane that relays the feed from TV motorbikes, were unable to get airborne.

Nibali started the day with a lead of 41 seconds over BMC Racing’s Cadel Evans, and more than doubles that now with the Astana rider picking up 12 bonus seconds for finishing in second place, plus the 33 seconds he gained over the Australian on the road.

Team Sky’s Rigoberto Uran, 2 minutes 4 seconds behind Nibali at the start of the day in third place overall, lost 41 seconds in total, and now lies just a second ahead of Santambrogio, who moved to fourth on GC.

Four breakaway riders who rejoined today’s original parcours with 20km left to ride had an advantage of five minutes at that point and had been part of an original break of seven that had got away 20km into the 180km stage following the start in Cervere.

The latter three – respectively Spanish, Dutch and American – crashed with 150km still to ride, leaving the other four members of the break, all of them Italian, out ahead on their own.

Two bike changes for Trentin inside the final 20km left Paolini, Pietropoli and Colbrelli out in front on their own, and over the following 5km the peloton, led by Team Sky working for Uran, only pulled back 10 seconds on them.

Into the final 5km, Pietropoli, who had been dropped, managed to rejoin Paolini and Colbrelli and with the GC group still more than 3 minutes further down the Jafferau, one of that trio looked set to be the winner on one of the toughest days of what has already been a hard race.

With 2km left, Pietropoli was in difficulties again, and this time there was no getting back, but any dreams Colbrelli or Paolini, winner of Stage 3 at Marina di Ascea that put him into the maglia rosa, might have had of prevailing today ended as those late attacks came from the GC group.

The amended route saw followed the planned parcours as far as Pinerolo, reached after 71.1km of riding, where instead of heading up to Sestriere, and its elevation of 2,048m, the riders headed on a 86.1km detour via the town of Susa, west of Turin.

It then rejoined the original itinerary at the junction for the road towards Bardonecchia, 20.1km short of the 1,908m summit of the Jafferau.

Likewise tomorrrow's stage is set to miss a much anticipated summit finish on the 2,642m Col du Galibier due to heavy snowfalls and a risk of avalanches.

The stage still looks like it will cross the French border but may finish at Valloire, a little after the climb of the Col du Telegraphe, which tops out at 1,566m, although the situation remains in flux and further changes may happen.

Interviewed on host broadcaster RAI shortly before the end of today’s stage, Michele Acquarone of organisers RCS Sport said that a final decision on tomorrow’s route will be taken tomorrow morning, and he also thanked the fans – many of them British – who had braved the conditions to make it to the finish today.

While the amended routes of this weekend's stages will have forced some of the GC contenders to change their tactics, one rider who won't have minded the revisions is points classification leader Mark Cavendish of Omega Pharma-Quick Step.

The changes put the Omega Pharma-Quick Step rider, winner of back-to-back stages in the past two days to take his total to four in this year's race, in perhaps a stronger position to aim to secure the red jersey in Brescia a week on Sunday.

That's perhaps the only guaranteed sprint stage left in the race, however, with a tough climb having to be negotiated towards the end of Wednesday's Stage 17 into Vincenza, but he'll have to do without the services of leadout man Gert Steegmans, who did not take to the start this morning.

Other riders who didn't sign on this morning were Blanco's Jack Bobridge, plus the Saxo-Tinkoff pairing of Daniele Bennati and Karsten Kroon.

Meanwhile, Garmin-Sharp's David Millar, wearer of the maglia rosa when the peloton paid a moving tribute to Wouter Weylandt the day after the Belgian's death two years ago, abandoned this year's race when he reached the feed zone today.

Also out of the race today after being taken to hospital after crashing were Enrico Battaglin of Bardiani Valvole-CSF Inox and Alessandro Vanotti, a key member of Nibali’s support team at Astana, who were reported to have respectively suffered broken ribs and a broken shoulder.

Born in Scotland, Simon moved to London aged seven and now lives in the Oxfordshire Cotswolds with his miniature schnauzer, Elodie. He fell in love with cycling one Saturday morning in 1994 while living in Italy when Milan-San Remo went past his front door. A daily cycle commuter in London back before riding to work started to boom, he's been news editor at road.cc since 2009. Handily for work, he speaks French and Italian. He doesn't get to ride his Colnago as often as he'd like, and freely admits he's much more adept at cooking than fettling with bikes.